Generally, in boats provided with an outboard engine, a steering wheel or tiller handle is used, as s steering operation member of a steering device, for steering the outboard engine mounted on a rear end portion of the body of the boat. Among the conventionally-known outboard engine steering devices is one which includes an assist mechanism provided between a steering wheel and a hydraulic helm pump (hydraulic steering pump), and in which steering force (operating force) of the steering wheel is assisted by the assist mechanism. One example of such a steering device is disclosed in Japanese Patent Application Laid-Open Publication No. 2005-231383 (hereinafter referred to as “the patent literature”). Because the steering wheel is provided on a front portion of the body (typically on an instrument panel) of the boat separately and at a considerable distance from the outboard engine, the assist mechanism and hydraulic helm pump can be provided near the steering wheel.
With the prior art steering device disclosed in the patent literature, as the steering wheel is operated, the steering force of the steering wheel is assisted by the assist mechanism, so that a drive shaft of the helm mechanism can be actuated with a relatively small steering force; namely, the necessary steering force of the steering wheel can be reduced by the provision of the assist mechanism. By the drive shaft of the helm mechanism being operated as above, oil is ejected from the helm mechanism and directed to a steering means, so that the steering means is actuated by the oil to steer the outboard engine.
However, the prior art steering device disclosed in the patent literature, where the helm mechanism is provided in axial alignment with the steering wheel and assist mechanism, would undesirably have a great total length from the steering wheel to the helm mechanism. Thus, a relatively great installation space would be required on and in the body of the boat for installing the prior art steering device. Therefore, the application of the prior art steering device disclosed in the patent literature is limited only to boats where a relatively great installation space can be secured on and in the body of the boat.
Also known are steering devices provided with a tiller handle, in which the tiller handle is connected, via a connection section, to the body of the outboard engine so that the outboard engine body can be steered by a human operator operating the tiller handle leftward or rightward. However, because the tiller handle is connected to the outboard engine body via the connecting section, it is difficult to provide the assist mechanism and helm mechanism near the tiller handle.